CVE-2026-31394: mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-03 · updated 2026-07-24
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations ieee80211_chan_bw_change() iterates all stations and accesses link->reserved.oper via sta->sdata->link[link_id]. For stations on AP_VLAN interfaces (e.g. 4addr WDS clients), sta->sdata points to the VLAN sdata, whose link never participates in chanctx reservations. This leaves link->reserved.oper zero-initialized with chan == NULL, causing a NULL pointer dereference in __ieee80211_sta_cap_rx_bw() when accessing chandef->chan->band during CSA. Resolve the VLAN sdata to its parent AP sdata using get_bss_sdata() before accessing link data. [also change sta->sdata in ARRAY_SIZE even if it doesn't matter]

Affected products

Linux kernel: from 6.11 before 6.12.78; from 6.13 before 6.18.20; from 6.19 before 6.19.10; 7.0-rc1, 7.0-rc2, 7.0-rc3, 7.0-rc4 — fixed in 6.12.78, 6.18.20, 6.19.10

How to fix

Upgrade to a fixed version: Linux kernel 6.12.78, 6.18.20, 6.19.10. Check the vendor advisory for mitigations.

References

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